1. Field of the Invention
The present invention relates to a method and appartus for accurately lowering the capacitance of a capacitor which is formed out of a pair of metallized dielectric film and more particularly to a laser and a controller are used to drill a plurality of a holes in a capacitor in order to trim its capacitance to an acceptable capacitance.
2. Description of the Prior Art
U.S. Pat. No. 3,892,023, entitled Process of Manufacturing a Capacitor Assembly, issued to George Warmont on July 1, 1975, teaches a method for making a capacitor assembly which is made up of any number of circular capacitors which are directly interconnected one to another while manufacturing is in progress, and the assembly thereof. A first capacitor is provided with adjacent plates thereof having their edges extending one beyond another. An insulating layer is wound around the first capacitor and a second capacitor is set on the layer. And so on until the wanted number of capacitors is reached. One side of the capacitor assembly, a mask is pushed into a recess provided at the edge of each insulating layer thereof. Both sides of the assembly are then metallized. The masks are removed leaving the required insulation between the various capacitors. The capacitor assembly may contain any number of capacitors, of the same or different capacitive values, in parallel or in series, housed in a single casing. U.S. Pat. No. 4,028,595, entitled, Multi-Voltage Capacitor Section, issued to Robert M. Stockman on June 7, 1977, teaches a method for making a multi-voltage capacitor. The method includes the steps of winding a single capacitor section in the usual manner from two metallized films and, after the winding has progressed through the proper number of turns for one of the capacitors, of removing the metallized layer from the surface of at least one film over a selected distance. The method also includes the steps of inserting an insulted sheet having a length sufficient to encircle the capacitor at least once between the film layer in order to extend beyond at least one end of the wound cylinder and of inserting the ends of two additional dielectric strips into the capacitor winding between the metallized films. The method further includes the steps of then completing the winding, of metal-plating each end of the wound section, and of attaching leads to the ends of the capacitor section resulting in a plurality of capacitor having different voltage ratings but wound within a single capacitor section. U.S. Pat. No. 3,921,041, entitled Dual Capacitor, issued to Robert M. Stockman on Nov. 18, 1975, teaches a dual metallized capacitor.
U.S. Pat. No. 4,348,714, entitled Multilayer Tubular Capacitor and Fabrication Thereof, issued to Clarence L. Wallace on Sept. 7, 1982, teaches a roll-up capacitor structure which is embodied by a carrier sheet and electrodes on the sheet. The electrodes have progressively increasing length along the sheet length dimension.
U.S. Pat. No. 3,921,041, entitled Multi-Section insulating sheet serves to blow molten metal out of the holes as they are formed and prevent metal from depositing on the metal plate around the holes.
U.S. Pat. No. 4,441,008, entitled Method of Drilling Ultrafine Channels through Glass, issued to Uck I. Chan on Apr. 3, 1984, teaches a method for generating ultrafine channels though and between opposed surfaces of a thin glass body by preheating the glass body to 500.degree. F.-1000.degree. F., and directing a beam of laser energy having a wavelength of at least about 10.6 microns along a fixed axis at the preheated body and against one of the surfaces for a period sufficient to melt and vaporize the portion of the glass in the path of the beam. The beam is defocused relative to the one surface and pulsed.
U.S. Pat. No. 4,286,250 also teaches an automatic system for producing laser formed resistor elements. The system includes a conventional X-Y positioner table which is mounted for two-dimensional movement in response to an X-direction servo drive motor and an Y-direction servo drive motor. Selective positioning of the table in response to the energization of the motors is provided by input signmals from a control unit. Positioned above the X-Y positioner table and also controlled selectively by the control unit is an argon laser. During use of the system a suitable plastic substrate is positioned on the table and moved thereby in a predetermined pattern with respect to a radiation beam produced by the argon laser. Impingement of the laser beam onto the substrate surface carburized resistor portions thereon having a pattern established by selective energization of the laser and movement of the table in accordance with the inputs from the control unit.
U.S. Pat. No. 4,476,375, entitled Process For Selective Cutting of Electrical Conductive Layer by Irradiation of Energy Beam, issued to Tsutomu Ogawa on Oct. 9, 1984, teaches a method for cutting an electrical conductive layer which has a heat-absorbing film deposited thereon by irradiating an energy beam on a portion of the electrical conductive layer intended to be cut. The energy beam is irradiated on the film so that the portion of the electrical conductive layer melts and alloys with the heat-absorbing film due to the energy absorbed and transferred by the heat-absorbing film.
U.S. Pat. No. 4,489,230, entitled Manufacturing Method for a Resistance Element, issued to Yutaka Yamamoto on Dec. 18, 1984, teaches a resistance element manufacturing method which forms on the surface of an electically insulating base layer including an organic material to be carbonized by irradiation of a laser beam. A laser beam transmitting electically insulating film is not carbonized by the irradiation of the laser beam. The laser beam is irradiated onto the base layer through the film from one side thereof so that it carbonizes the irradiated portion of the base layer in order to form a resistence layer.
U.S. Pat. No. 4,286,250, entitled Laser Formed Resistor Elements, issued to Peter J. Sacchetti on Aug. 25, 1981, teaches a laser formed resistor element which includes a body element having an organic substrate portion and a laser formed, resistor portion carburized thereon. A first electrical conductor is electrically connected to one location on the resistor portion so as to form one terminal for connection to an electrical circuit and a second electrical conductor is electrically connected to the resistor portion at a different location so as to form another terminal for connection to the electrical circuit.
U.S. Pat. No. 3,404,032, entitled Method of Making Film Resistor, issued to Franklin M. Collins on Oct. 1, 1968, teaches a method for adjusting the value of a resistor including a conductive film of thallium oxide dispersed in glass according to which the film is selectively heated in localized areas to render portions of the film comparatively non-conductive.